High current switch



Oct. 18, 1955 A. M. DAILY m-AL 2,721,243

HIGH CURRENT SWITCH Filed April 5, 1954 2 Sheets-Sheet l I I I mdwgmi Arihur M D512 515212)? N Gal 5 15 mm w '7' Oct. 18, 1955 A. M. DAILY ETAL HIGH CURRENT SWITCH 2 Sheets-Sheet 2 Filed April 5, 1954 ,8 7 All lndw mt Ari 227.1? M .275 1 United States Patent HIGH CURRENT SWITCH Arthur M. Daily, Edwardsburg, Mich, and Sidney W. Gallay, Elkhart, llnd., assignors to Chicago Telephone Supply Corporation, Elkhart, 1nd,, a corporation of Indiana Application April 5, 1954, Serial N0. 420,798

' 1 Claim. (Cl. 200166) This invention relates to electric switches and has as its purpose to provide an electric switch especially well adapted for use as an on-oif switch for color television receivers.

The on-off switch of a color television receiver must be capable of handling currents of considerably greater magnitude than those encountered in radio and ordinary black and white television. This follows from the fact that compared to ordinary black and white television receivers, color television receivers have many more components in order to handle the three primary colors used in the reproduction of the transmitted signal, and all of these draw current when the set is turned on. To meet this increased load the present invention provides a switch with two parallel-connected sequentially closed sets of contacts, both of which are closed when the receiver is in operation, and one of which always makes and breaks the load circuit. As a result there is never any arcing at the other set of contacts to impair its low contact resistance.

An important object of this invention is to embody this concept of sequentially engaged multiple sets of contacts without increasing the overall size of the switch and in a manner which does not deviate from the basic switch design and construction found in Patent No. 2,286,162, so that the improvement sought is achieved without entailing serious revisions in existing tooling and assembly practices. This objective is accomplished by having both sets of contacts provided by a single bridging contactor and only one pair of stationary contacts cooperating in a novel manner.

With the above and other objects in view, which will appear as the description proceeds, this invention resides in the novel construction, combination and arrangement of parts substantially as hereinafter described and more particularly defined by the appended claim, it being understood that such changes in the precise embodiment of the hereindisclosed invention may be made as come within the scope of the claim.

The accompanying drawings illustrate one complete example of the physical embodiment of the invention constructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view partly in side elevation and partly in longitudinal section showing an on-oif switch embodying this invention mounted on the back of a variable resistor;

Figure 2 is a front view of the switch shown detached from the variable resistor and in its switch-open condition;

Figure 3 is a view similar to Figure 2 but showing the switch closed;

Figure 4 is a detail sectional view through the contactor and the adjacent parts of the switch, taken generally on the planes of the line 44 in Figure 3, said view illustrating the parts substantially at the instant of initial closure of the switch by engagement of the first-toclose set of contacts;

Figure 5 is a view similar to Figure 4 but showing the switch in its fully closed condition with both sets of contacts engaged;

Figure 6 is a perspective view of only the contactor and stationary contacts of the switch and illustrating the same in their final switch-closed relationship;-and

Figure 7 is a developed plan view of the blank from which the contactor of the switch is formed.

Referring now more particularly to the drawings, the numeral 3 designates generally the switch of this invention, shown mounted upon the back of a variable resistor 4. As is customary, the switch and the variable resistor are operable by a common shaft 5 which enters the front wall of the resistor housing to drive its rotatable contactor mechanism (not shown). The contactor mechanism includes an arm 6 which coacts with a switch tripping cam 7 to actuate the switch mechanism during part of the travel of the contactor. To this end the cam is so located that it enters the housing of the resistor through an opening 8 in its rear wall 9 for coaction with the arm 6.

l n its basic design the switch 3 is similar to the switch of Patent No. 2,286,162, and hence is contained within a cylindrical housing having a flat end wall 10 of insulating material which provides the base of the switch, and a metal side wall 11, the latter having tangs 12 by which the switch housing is secured to the back wall of the resistor housing. A pair of stationary contacts 13 are mounted on the base to be electrically bridged by a contactor 14, the design and construction of which constitutes one of the chief considerations of the invention. The stationary contacts have the usual terminals 15 by which the switch is connected in the circuit to be controlled.

The contactor 14 is essentially a resilient U shaped metal band constrained to slide across the base of the switch with its open end facing the stationary contacts to and from a switch closed position at which its legs engage and electrically bridge the stationary contacts. The contactor is constrained to its path of motion by being connected to a segment-like drive arm 16 which overlies the base and the contactor, and is pivoted on a post P to swing through an angle sufiicient to carry the contactor to and from its switch-closed position. This angle is approximately twenty-five degrees and is defined by the engagement of the arm 16 with the side wall 11 of the switch housing as shown in Figure 2, and the engagement of the contactor with the stationary contacts as shown in Figure 3.

The connection of the contactor 14 with its drive arm 16 comprises a lug 17 on the closed end or bight of the U shaped contactor eXtending upwardly therefrom and fitting loosely in an opening 18 in the drive arm and a pair of opposite upwardly projecting lugs 19 on the legs of the contactor and received in an opening 20 in the drive arm. As will be described later the relative positions of these lugs and the size of the openings in which they are received is such that as the switch is closed the contactor is free to adjust itself to the stationary contacts.

A torsion spring 21 connects the switch tripping cam 7 and the drive arm 16 in the manner fully described in the aforesaid Patent No. 2,286,162, and attention is directed to the fact that as the cam 7 is driven from one position to the other the spring 21 has an over-center snap action to snap the contactor to and from its switch closed position. It is also important to observe that the spring 21 exerts a downward as well as a lateral force on the drive arm 16 and the contactor therebeneath.

To the extent thus far described, the switch of this invention is substantially the same as that of the aforesaid patent. However, where the switch of the patent had but one set of contacts between which the circuit was made and broken, the switch of this invention has two sets of parallel connected sequentially engaged contacts. To this end the lugs 19 which extend upwardly from the legs of the U shaped contactor are laterally and outwardly offset with relation to the adjacent portions 22 of the contactor legs and these offset portions of the lugs 19 have downwardly facing contact surfaces 23 positioned to engage and slide onto the top surfaces 24 of the stationary contacts to provide one of the two sets of contacts while the outer sides of the leg portions 22 which converge towards each other engage the cylindrical sides of the contacts 13 to provide the other set of contacts.

The location of the downwardly facing contact sur faces 23 with respect to the contact surfaces provided by the outer sides of the leg portions 22, is such that during closure of the switch the latter come into switch closing engagement with the stationary contacts before the former engage the contacts. In other words, the downwardly facing contact surfaces or portions 23 are spaced back from the converging outer ends of the legs of the U shaped contactor a distance such to assure the desired sequential engagement of the two sets of contacts which this construction provides.

To enable the contact portions 23 to ride up onto the top surfaces 24 of the stationary contacts, the offset lugs 19 have their undersides inclined as at 25. Hence, as the contactor moves toward switch-closed position and the converging contact surfaces provided by the leg portions 22 are wedged between the facing cylindrical surfaces of the stationary contacts, the inclined undersides 25 of the lugs 19 will first engage the edges of the stationary contacts 13 and then ride up thereon until the contactor comes to rest with its contact portions 23 seated fiat upon the tops 24 of the stationary contacts.

It is, of course, possible when the switch is new and the contact surfaces are not worn that the contactor may come to rest before its downwardly facing horizontal contact surfaces 23 seat flat upon the tops of the stationary contacts. In any event however, it will be clear that both sets of contacts will be firmly engaged when the contactor comes to rest and that both sets of contacts have an appreciable wiping engagement during opening and closure of the switch with the greatest wiping action taking place at the set of contacts provided by the vertical outer sides of the leg portions 22 and the cylindrical sides of the stationary contacts. This, of course, is desirable since it is this set of contacts between which initial closure and final opening of the switch takes place.

The effect of any arcing which occurs during opening of the switch is thus not only limited to one of the two sets of contacts but is confined to that set of contacts where the wiping action is greatest. Consequently, the surfaces of these contacts, which may be referred to for convenience as the horizontal contacts since their surfaces are substantially parallel to the base, will always be clean and have low contact resistance, and as a result, the heat which must be dissipated inside the switch will be well within the limits set by Underwriters Laboratories for approval.

By actual test it has been found that the switch of this invention has a capacity two to two and one-half times greater than a switch like that of the aforesaid Patent No. 2,286,162, mounted in a housing of the same diameter.

As best shown in Figure 4, the entire bottom edge of the contactor lies in a common plane, and except when the switch is in its closed condition (shown in Figure this bottom edge of the contactor is held flat against the base by the downward thrust of the spring 21. The downward thrust of the spring is transmitted from the drive arm 16 onto the contactor without seriously interfering with the freedom of the contactor to adjust itself to the stationary contacts as the switch closes because the underside of the drive arm has only line contact engage- A. ment with inclined portions 26 of the top edge of the contactor flanking its lug 17, and two small areas 27 at the extremities of the legs of the contactor.

The sliding engagement of the bottom edge of the contactor with the top of the base which obtains throughout the major part of the travel of the contactor to and from switch closed position does not interfere with the freedom of the contactor to adjust itself to the contacts because during the final switch closing travel when the inclined rndersides 25 of the second-to-be engaged set of contacts rides onto the stationary contacts, the contactor is lifted off the base as shown in Figure 5.

Another feature of the construction which contributes to the freedom of the contactor to adjust itself to the stationary contacts lies in the fact that during closure of the switch the contactor is driven forward by the engagement of the rounded back of the lug 17 with the adjacent side of the hole 18 in the arm. Hence, the contactor is free to rock about the lug 17 as soon as its width is slightly reduced by the wedging of the ends of its legs between the facing convex surfaces of the contacts, for at this instant, the lugs 19 leave the adjacent sides of the opening 20 in the drive arm.

During the opening of the switch, upstanding shoulders 28 on the end portions of the contactor legs are engaged by the adjacent edge of the opening 20 so that the switch opening force imparted to the contactor by the drive arm is applied directly adjacent to the engaged contacts. The distance between the outer face of the lug 17 and a straight line joining the shoulders 28 is slightly less than the distance between the remote sides of the openings 18 and 20. Hence, during switch closure the shoulders 28 are clear of the adjacent side of the opening 20 so as not to interfere with the then existing lateral freedom of the contactor.

As shown in Figure 7 the contactor 14 is formed up from a simple symmetrical stamping consisting essentially of a band of sheet metal having a central upstanding lug which becomes the lug 17, and two other lugs flanking the first lug to provide the lugs 19 and also the shoulders 28. During the blanking operation these outer lugs are slit as at 30 to permit offsetting and shaping the lugs 19 as described.

From the foregoing description taken in connection with the accompanying drawing it will be readily apparent that this invention provides an electric switch especially well adapted for use with color television receivers in that it greatly increases the current carrying capacity of the switch without necessitating any increase in its overall size. It will also be apparent to those skilled in the art that although the broad general concept of sequential engagement of multiple sets of switch contacts is old, the application of this expedient in the manner described to a switch especially designed for use in television and radio receivers is new.

What we claim as our invention is:

A contactor for an electric switch comprising: a U- shaped resilient band providing spaced apart legs, the bottom edges of which lie substantially in a common plane and the oppositely facing outer side surfaces of which are perpendicular to said plane, said legs having outwardly offset portions spaced above their bottom edges and back from their outer ends; the undersides of the rearwardmost parts of said offset portions which are farthest from the outer ends of the legs lying substantially in a common plane parallel to the plane of the bottom edges of the legs so that said undersides of said parts of the offset portions provide a pair of downwardly facing contact surfaces while the oppositely facing outer sides of the legs provide another pair of substantially perpendicular contact surfaces, and the undersides of the forwardmost parts of said offset portions being inclined upwardly to provide camming surfaces leading to the downwardly facing contact surfaces.

(References on following page) Petersen May 19, 1931 Bell Dec. 17, 1935 6 Schellenger June 9, 1942 Alden Aug. 4, 1942 FOREIGN PATENTS Great Britain Feb. 22, 1895 

